1. Department of Information Engineering, University of Padova, via Gradenigo 6B, 35131 Padova, Italy
2. CNR—IFN UOS Padova, Via Trasea 7, 35131 Padova, Italy
3. Experimental Physics of EUV, JARA-FIT, RWTH Aachen University, Steinbachstr. 15, 52074 Aachen, Germany
4. CNR- Istituto Officina Materiali, I-34149 Trieste, Italy
5. Chair for the Technology of Optical Systems (TOS), JARA-FIT, RWTH Aachen University, Steinbachstr. 15, 52074 Aachen, Germany
6. Central Facility for Electron Microscopy (GFE), JARA-FIT, RWTH Aachen University, Ahornstr. 55, D-52074 Aachen, Germany
7. Institute of Precision Optics Engineering, Tongji University, Shanghai 200092, China
8. Peter Grünberg Institut (PGI-9), JARA-FIT, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany